Engineering - Mechanisms

EN115 Engineering Concepts

Mechanisms

Build one of the following mechanisms in WM.

Mechanism Presentation Instructions:
Appearance instructions:

Make the background a dark color. View | Background Color
Turn grid lines off. View | Workspace | Gridlines
Turn all tracking off except for the point of interest. Edit | Select All; Window | Appearance | (Uncheck tracking boxes. )
Select the point of interest. Window | Appearance | (Check tracking boxes for this point. )
Label all parts and pins!

Have Working Model graph the required quantities:
First Select the desired element with your mouse;

Measure | Position* or Measure | Velocity
Clicking on the upper left corner arrow in the measurement window changes the type of graph.
(toggles between bar graph, digital readout, graph). Pick the graph.
You can select the graph and then: windows | appearance to customize it
Be ready to discuss the shape of your graph.

*If the "position" option does not come up after selecting your point, create a new point near the one you want to measure; then "measure | position" for it.

Whitworth Quick-Return Linkage

Member DE = 13.5in; Member DCB = 12in; Member AB = 3.2in; A is 2.7in below C; Distance CD = 4in; A is a motor with velocity 60 deg/sec; C is fixed, 10in from E; Arm DCB is slotted; E slides in the slot. To put a slot on DCB-select DCB, then use the gray slot tool. Put E at (0,0). Measure the X Pos. and Vel. of Pin E vs. time.

4 bar linkage

Motor A @ (0,0) mm; Pin D @ (180,0) mm; Link AB = 100 mm; Link BC = 260 mm; Link CD = 180 mm; Motor @ A = 60 deg/sec. Measure the X,Y pos. and vel. of Pin C vs. time.

Candy Wrapping Mechanism

AC = 8 in; BD = 7.0 in; CD = 2.3 in; DE = 2.5 in; EF = 1.9 in; FG = 2.3 in; GH = 3.8 in; Rocker arm HGF is 90 degrees (you may square pin two rectangles to create HGF); Motor at A = 60 deg/sec; Fixed point A is at (0,0); fixed point C at (8,0);fixed point G at (3.6,-0.9) The motion of point H is to feed paper into a candy wrapping machine. Measure the X,Y Pos. and Vel. of Pin H vs. time.

Straight line mechanism

LB = LDM = 2 m; SL = PD = DM = 0.5 m; BO = MO = PO = 1 m; Motor S velocity = 30 deg/sec; (Start SL slightly off vertical to make it run. ); and P is fixed. Put S at (0,0). S and P have the same y coord. Dimensions are critical; make sure the points are at the end, in the middle of the member. Measure X position and velocity of B vs. time.

Scotch Yoke

Horizontal member = 0.7 m by 4 m; Vertical member = 1 m by 5 m; Vertical slot in vertical member (use gray slot tool); Hold the mechanism in place using a horizontal square pin slot; Motor at A (left end of yellow rod) connected by 0.2 m by 2m link to slot. Put the motor at (0,0). Measure X pos. and vel. of horizontal bar vs. time.

Assembly line mechanism

Motor at M 0.5 rev/sec. A is fixed. Vertical piston at D slides on horizontal square slot; it is attached to arm CD with a round pin. ABD is one piece. (You may lock two pieces together with a square pin if you like. ) Center D at (0,0). Measure X position and velocity of the piston at D vs. time.

Stirling Engine

Pistons rididly attached to yellow and orange members connected to L piece which is rigidly attached to the wheel. Pistons slide on square slots. Wheel fixed, revolves at 10 rev/min. Put the large piston at (0,0). In the actual engine, fuel is ignited between pistons to drive the wheel. Measure X position of each piston vs. time.

Watt Parallel Motion Engine

Rocker arm fixed at its center. Piston slides on square slot. Wheel driven by motor, 10 rev/min. Connecting rod fixed at left end; attached to mechanism as shown. Put the piston at (0,0). In the actual engine, steam drives the piston which drives the wheel. Measure y position and velocity of the piston vs. time.

Oil Pump

Motor link radius = 0.6 m; Connecting link = 2.91 m to upper left corner; Main beam = 6.3 m by 1 m; Pivot = 3 m from left end; 0.1 m from bottom; Motor at end of short link velocity = 1 rev/sec; Put A at (0,0). Measure the Y pos. and vel. of pin A vs. time.

Power hacksaw

Wheel radius = 100 mm; Motor speed = 60 rev/min; Arm length = 450 mm; Hacksaw blade centered at origin; Blade is 450 by 200 mm comprised of four members each 20mm thick. Put the top center of the blade at (0,0). Measure X pos. and vel. of blade vs. time.

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